The artificial sweetener 4,1′, 6′-trichloro-4,1′, 6′-trideoxygalactosucrose (“sucralose”) is derived from sucrose by replacing the hydroxyls in the 4, 1′, and 6′ positions with chlorine. A number of different synthesis routes for the preparation of sucralose have been developed in which the reactive hydroxyl in the 6 position is first blocked, as by an ester group, prior to the chlorination of the hydroxyls in the 4, 1′, and 6′ positions, followed by hydrolysis to remove the ester substituent to produce sucralose. Several of these synthesis routes involve tin-mediated synthesis of sucrose-6-esters.
Sucrose-6-esters may be chlorinated, such as, by the process of Walkup et al. (U.S. Pat. No. 4,980,463, which is incorporated herein by reference in its entirety). The chlorination process produces as a product a sucralose-6-ester, such as 4,1′,6′-trichloro-4, 1′,6′-trideoxygalactosucrose-6-acetate, in solution in a tertiary amide, typically DMF, plus salts (produced as a result of neutralizing the chlorinating agent after completion of the chlorination reaction), chlorination reaction byproducts, and other impurities. Exemplary chlorination reaction byproducts include chlorinated carbohydrates other than sucralose, such as mono- and di-chlorinated sucrose, as well as other forms of chlorinated sucrose.
Conventionally, after a neutralization step, a raw material for sucralose production, i.e., the tertiary amide reaction vehicle (e.g., DMF) for the chlorination reaction, as well as liquid waste/byproduct of the sucralose production process, may be removed, such as, by steam distillation. Such waste composition may contain DMF (e.g., about 45-50%), methanol (e.g., about 25-30%), water (e.g., about 20-25%), and other organic and/or inorganic compositions. Traditionally, DMF is recovered and recycled from the waste liquid using a multi-tower distillation system, which is capable of purifying DMF up to 99.95% pure and has a recovery rate up to 80%. The recovered DMF may be re-used in sucralose production. However, such multi-tower distillation systems occupy a large area and expensive to use.
Another raw material for sucralose production is sucrose. Since the existent of water interferes with the chlorination process, sucralose manufacture requires the use of anhydrous sucrose, which may be obtained by purchasing high grade anhydrous sucrose from a commercial supplier or drying ordinary sucrose under vacuum condition. However, neither option is optimal because: (1) anhydrous sucrose is very expensive (about 30% higher than the best ordinary first grade sucrose); and (2) the vacuum drying is costly, time-consuming, and labor intensive.
Therefore, there exists a need for effective, efficient, and economical methods and systems for preparing raw materials (e.g., DMF and anhydrous sucrose) used in sucralose production.